Mobile terminals typically include a display device, such as a liquid crystal display (LCD). When a user attempts to view an image stored in the mobile terminal or image data inputted from a camera, the mobile terminal converts the input image data into a RGB (Red-Green-Blue) or YUV (e.g., PAL system) signal, adjusts the converted signal according to a gray level of brightness, and differentially applies a voltage corresponding to the RGB or YUV signal by the gray level, thereby displaying the image data on the LCD. Normally, the YUV signal has 16 bits, 18 bits or 24 bits. When the converted YUV signal has 18 bits, the gray level number of the YUV signal is 512.
FIG. 1 is a graph showing a relationship between gray levels and input voltages.
Referring to FIG. 1, when an YUV signal inputted to an LCD having a predetermined γ value has 18 bits, the voltages inputted by the gray levels increase by the rise of the gray levels. In a typical display device, a γ curve may be represented by ‘y=xγ’, and in the case of a cathode ray tube (CRT) monitor, a γ curve has a γ value of ‘2.2’.
Generally, the γ curve is used to display externally-inputted image data on the LCD, and is provided by the manufacturer of the display device. In addition, the γ curve, which is based on the γ value, is used to vary the input voltage according to the brightness level of the input image data.
FIG. 2 is a graph showing a relationship between gray levels and input voltages in each gray level.
Referring to FIG. 2, the input voltages linearly increase according to the number of the gray levels. For example, FIG. 2 shows gray levels 256 and 257, out of a maximum 512 gray levels. A voltage of V1 is inputted in gray 256 and a voltage of V2 is inputted in gray 257.
However, the voltages inputted by the gray levels are restricted regardless of the brightness values of the image signal. Moreover, since the input voltages are restricted due to the linear increase of the γ curve, the brightness of the real image does not completely match the γ curve. As a result, the image displayed on the LCD is different from the real image.